/*
// Licensed to Julian Hyde under one or more contributor license
// agreements. See the NOTICE file distributed with this work for
// additional information regarding copyright ownership.
//
// Julian Hyde licenses this file to you under the Apache License,
// Version 2.0 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 */
package org.olap4j.mdx;

import org.olap4j.impl.Olap4jUtil;
import org.olap4j.type.*;

import java.io.PrintWriter;
import java.math.BigDecimal;

/**
 * Represents a constant value, such as a string or number, in a parse tree.
 * 
 * <p>
 * Symbols, such as the <code>ASC</code> keyword in <code>Order([Store].Members, [Measures].[Unit Sales], ASC)</code>,
 * are also represented as Literals.
 * 
 * <p>
 * A LiteralNode is immutable.
 * 
 * @author jhyde
 */
public class LiteralNode implements ParseTreeNode {

	// Data members.

	private final Object value;
	private final Type type;
	private final ParseRegion region;

	/**
	 * Private constructor.
	 * 
	 * <p>
	 * Use the creation methods {@link #createString} etc.
	 * 
	 * @param region
	 *            Region of source code
	 * @param type
	 *            Type of this literal; must not be null
	 * @param value
	 *            Value of this literal, must be null only if this is the null literal
	 */
	private LiteralNode(ParseRegion region, Type type, Object value) {
		assert type != null;
		assert (type instanceof NullType) == (value == null);
		assert (type instanceof StringType || type instanceof SymbolType) == (value instanceof String);
		assert (type instanceof NumericType) == (value instanceof BigDecimal);
		this.region = region;
		this.type = type;
		this.value = value;
	}

	/**
	 * Creates a literal with the NULL value.
	 * 
	 * @param region
	 *            Region of source code
	 * @return literal representing the NULL value
	 */
	public static LiteralNode createNull(ParseRegion region) {
		return new LiteralNode(region, new NullType(), null);
	}

	/**
	 * Creates a string literal.
	 * 
	 * @param region
	 *            Region of source code
	 * @param value
	 *            String value
	 * 
	 * @return literal representing the string value
	 * 
	 * @see #createSymbol
	 */
	public static LiteralNode createString(ParseRegion region, String value) {
		if (value == null) {
			throw new IllegalArgumentException("value must not be null");
		}
		return new LiteralNode(region, new StringType(), value);
	}

	/**
	 * Creates a symbol literal.
	 * 
	 * @param region
	 *            Region of source code
	 * @param value
	 *            Name of symbol
	 * 
	 * @return literal representing the symbol value
	 * 
	 * @see #createString
	 */
	public static LiteralNode createSymbol(ParseRegion region, String value) {
		if (value == null) {
			throw new IllegalArgumentException("value must not be null");
		}
		return new LiteralNode(region, new SymbolType(), value);
	}

	/**
	 * Creates a numeric literal.
	 * 
	 * @param region
	 *            Region of source code
	 * @param value
	 *            Value of literal; must not be null
	 * @param approximate
	 *            Whether the literal is approximate
	 * 
	 * @return literal representing the integer value
	 */
	public static LiteralNode createNumeric(ParseRegion region, BigDecimal value, boolean approximate) {
		if (value == null) {
			throw new IllegalArgumentException("value must not be null");
		}
		Olap4jUtil.discard(approximate); // reserved for future use
		return new LiteralNode(region, new NumericType(), value);
	}

	public <T> T accept(ParseTreeVisitor<T> visitor) {
		return visitor.visit(this);
	}

	public Type getType() {
		return type;
	}

	public ParseRegion getRegion() {
		return region;
	}

	/**
	 * Returns the value of this literal.
	 * 
	 * <p>
	 * Value is always of type {@link String} (if the literal is a string or a symbol), of type
	 * {@link java.math.BigDecimal} (if the literal is numeric), or null (if the literal is of null type).
	 * 
	 * @return value
	 */
	public Object getValue() {
		return value;
	}

	public void unparse(ParseTreeWriter writer) {
		PrintWriter pw = writer.getPrintWriter();
		if (value == null) {
			pw.print("NULL");
		} else if (type instanceof SymbolType) {
			pw.print(value);
		} else if (type instanceof NumericType) {
			pw.print(value);
		} else if (type instanceof StringType) {
			pw.print(MdxUtil.quoteForMdx((String) value));
		} else {
			throw new AssertionError("unexpected literal type " + type);
		}
	}

	public LiteralNode deepCopy() {
		// No need to copy: literal nodes are immutable.
		return this;
	}

}

// End LiteralNode.java
